1. Field of the Invention
The present invention relates to a high-frequency circuit device in a transmission/reception part of a high-frequency radio set, specifically, a mobile communication apparatus such as a mobile phone or the like. More specifically, this invention relates to a multiband high-frequency circuit device including a semiconductor amplifier circuit (hereinafter, referred to as a transmission amplifier circuit) for high-frequency power transmission and a switch circuit for switching among a plurality of frequency bands.
2. Description of the Related Art
Under a system according to a W-CDMA (Wideband-Code Division Multiple Access) system or a CDMA (Code Division Multiple Access) system such as is used for a mobile phone or the like, some types of mobile phones use a plurality of frequency bands including frequency bands that differ by not less than 200 MHz from each other, for example, 2 GHz in combination with 1.7 GHz, the frequency band of 1.4 to 1.5 GHz, or the frequency band of 800 to 900 MHz. In such a mobile phone, a transmission amplifier circuit that transmits high-frequency power from an antenna is configured using separate high-frequency amplifiers with respect to the respective frequency bands for the following reason. That is, when a conventional linear high-frequency amplifier that receives a quadrature modulation signal is operated to perform a linear amplification operation on a wide frequency band, the current consumption increases considerably.
Furthermore, in the case where a wireless LAN (Local Area Network) function is imparted to a mobile phone, not only because this function is added but also because frequencies in the frequency band of 2.4 GHz and the frequency band of 5 GHz are used in this case, the number of high-frequency amplifiers to be used should be increased by the number of the frequency bands, which has been disadvantageous.